Katowice, Poland -- Sixty-seven people died and more than 80 were hospitalized when the roof of an exhibition center in this southern Polish city collapsed Saturday apparently under the weight of heavy snowfall.An estimated 700 people attending a carrier pigeon show were inside the 108,000-square-foot International Katowice Fair when the roof caved in suddenly, according to authorities.An investigation into the roof failure and possible structural flaws to the building continues, but authorities said a preliminary investigation indicates that a buildup of snow on the roof triggered the disaster.The authorities said that center management had allowed about twice the amount of snow than legally permitted to accumulate on the roof.However, a lawyer representing the center's operator, London-based Expo Media Group, said the snow had been cleared.In a statement, Expo Media expressed "deepest sympathy to the family, relatives and friends of those involved in this devastating circumstance" and pledged "to continue to work closely with the City of Katowice, the Polish State Treasury and the related investigating authorities, providing any necessary information required."The center will remain closed until further notice, the company said.